1. Field of the Invention
This invention relates to a weather strip to be attached to a peripheral part of a door opening of a vehicle and the like as well as to a method for producing the same.
2. Related Art
In general, a weather strip is provided on a peripheral part of a door opening and a peripheral part of a door of a vehicle such as an automobile. The weather strip is provided with an attachment base (a trim part having a section in a substantially U-shape, for example) to be attached to an attachment part (flange, for example) provided on the vehicle door opening peripheral part and the vehicle door opening peripheral part and a sealing part provided as being projected from the attachment base and having a hollow part. When the door is closed, the sealing part is brought into pressure-contact with the door peripheral part, the door opening peripheral part, and the like, so that a seam between the door and the vehicle body is sealed.
The weather strip is molded from a synthetic rubber excellent in weather resistance, such as EPDM (ethylene-propylene-diene copolymer). Almost all of weather strips are made from the above-described rubber material and provided with an extruded part that is molded by conventional extruding methods. The extruded part is obtainable by vulcanizing an intermediate molded body that is extruded from an extruder in a non-vulcanized state.
In general, the sealing part is formed from a sponge material, and a technology of forming a superficial part of the sealing part from a material that is harder than other parts has been known (for example, a solid rubber is used for the superficial part of the sealing part while using a sponge rubber for the other parts). However, it is in fact difficult to uniformly form a thin and wide solid layer made from a solid rubber on the superficial part by extruding. Accordingly, there is a fear that the solid layer is increased in thickness leading to an increase in thickness of the sealing part to result in undesirably large increase in repulsion force (reactive force against the door) of the sealing part.
Also, a technology of irradiating a non-vulcanized and non-foamed intermediate molded body (the attachment base, for example) with an electron beam to crosslink the superficial part of the intermediate molded body in the non-foamed state and then vulcanizing/foaming the rest of parts in molding the weather strip (extruded part) having the sponge rubber part has been known (see JP-A-10-52867, for example). By employing the technology, it is possible to form the solid layer on the superficial part of the sponge rubber part, thereby enhancing durability and the like of the sponge rubber part.
Though it is possible to achieve the solid layer thinner than that obtained by the simultaneous formation of the solid layer by employing the technology disclosed in JP-A-10-52867, the technology is not yet satisfactory since there is a fear for inviting the increase in reactive force in the case of the above-described sealing part.
Further, with the technology disclosed in JP-A-10-52867, there is a fear that, even when only the sealing part is irradiated with the electron beam with a region (trim part, etc.) except for the sealing part is being masked, the masked part such as a peripheral portion of the sealing part, for example, can be crosslinked in addition to the sealing part. More specifically, since it is difficult to properly define the part to be hardened by the electron beam irradiation, there is a fear that the parts that do not require the increase in rigidity can be increased in rigidity. Also, since an apparatus for the electron beam irradiation is required, an equipment cost can be remarkably increased.